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The orbit of asteroid 2011 AG5 carries it beyond the orbit of Mars and as close to the sun as halfway between Earth and Venus.CREDIT: NASA/JPL/Caltech/NEOPO

An asteroid discovered last year has been gaining notoriety because of a chance that it could hit Earth in 28 years, but NASA scientists say the odds are extremely remote that it will pose any danger to us.

The huge space rock, called asteroid 2011 AG5, is about 460 feet (140 meters) wide and circles the sun on a path between the orbits of Mars and Venus. Astronomers spotted it on Jan. 8, 2011 using the 60-inch Cassegrain reflector telescope on Mount Lemmon north of Tucson, Ariz., with some projections suggesting the odds of an Earth impact are 1 in 625.

Yet currently, the asteroid is rated a 1 on the 1-10 Torino Impact Hazard Scale that denotes potentially dangerous asteroids (1 is the least hazardous rating), NASA scientists say. So while there is a slight chance that asteroid 2011 AG5 could impact our planet in 2040, astronomers still need much better observations to define its orbit.

“Because of the extreme rarity of an impact by a near-Earth asteroid of this size, I fully expect we will be able to significantly reduce or rule out entirely any impact probability for the foreseeable future,” said Don Yeomans, manager of NASA’s Near-Earth Object Program Office at the Jet Propulsion Laboratory in Pasadena, Calif., in a statement.

The space rock is currently located in the daytime sky, so astronomers cannot make more observations from Earth until its orbit swings into the nighttime sky. That will occur in a next year, Yeomans said.

“In September 2013, we have the opportunity to make additional observations of 2011 AG5 when it comes within 91 million miles (147 million kilometers) of Earth,” Yeomans said. “It will be an opportunity to observe this space rock and further refine its orbit.”

The asteroid is also expected to come near Earth in February 2023, but it will pass no closer than about 1 million miles (1.6 million kilometers). Then again in 2028, 2011 AG5 will be in the area, but it won’t come within about 10.4 million miles (16.7 million kilometers) of our planet.

The pull of Earth’s gravity during this pass, however, will have the chance of setting the rock on a more direct collision course that could target the asteroid to slam into our planet on Feb. 5, 2040.

Still, the odds of this occurring are remote, scientists say. The asteroid’s 1-in-625 chance of posing a threat to Earth is not expected to last.

“It is important to note that with additional observations next year the odds will change and we expect them to change in Earth’s favor,” Yeomans said.

This asteroid is just one of 8,744 near-Earth objects that have been discovered. NASA’s Near-Earth Object Observations Program detects and studies these rocks to keep a vigilant lookout for any that might pose a threat to us.

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Asteroid 2012 DA14 is making headlines this week, despite the fact that the “incoming” space rock, as it has been described, definitely won’t hit Earth.

The 150-foot-wide space rock will pass within 17,000 miles (27,000 kilometers) of us next February. That’s nearer than the orbits of some geosynchronous satellites, and the closest shave of a mid-size asteroid ever predicted before the actual flyby has occurred. But even so, NASA assures the world that there is no chance of asteroid 2012 DA14 hitting Earth next year. Zero, zip, zilch.

Why, then, all the terror about this unthreatening space rock? And why the recent doom and gloom about another space rock, the big asteroid 2011 AG5, a football-field-size rock that NASA says will almost certainly not collide with the planet in 2040? Don Yeomans, head of the Near-Earth Object Observations Program at NASA’s Jet Propulsion Laboratory, blames the upsurge in asteroid panic on two main factors.

“One problem is that the Internet is wide open to anyone to say anything,” Yeomans told Life’s Little Mysteries, a sister site to SPACE.com. In the past, claims about asteroids were written up by scientists and submitted to peer-reviewed journals, a critical process that “would filter out nonsense,” he said. “If something was published, it was reliable.”

But today, hundreds of scary blurbs about the latest asteroid get written and posted to blogs and tabloid-like sites before NASA scientists can vet the claim and publish their official, less-terrifying statement regarding the asteroid’s trajectory.

“In the case of this asteroid, you get hundreds of hits on the Internet, and in the case of the 2012 [Mayan calendar] business, millions of hits suggesting disaster. And you get a few folks in the media and at NASA who put out the truth. But people go online and see millions about disasters and a few saying ‘no disaster’ and they think, well, the majority of these say I should be worried,” Yeomans said.

The other half of the problem is that many people do not know how to judge the validity of the pseudo-scientific information they read. “There are millions of people out there who have not been trained in the scientific method, and don’t understand that evidence is critical for supporting any new idea — especially any dramatic departure from the current state,” he said.

In psychology, this is known as the Dunning-Kruger effect. People who lack knowledge in a given area, such as science, are unable to accurately assess their own abilities in that area, and so they aren’t aware that they are coming to blatantly false conclusions.

David Dunning, a psychologist at Cornell University who first characterized the phenomenon, recently explained, “Many people don’t have training in science, and so they may very well misunderstand the science. But because they don’t have the knowledge to evaluate it, they don’t realize how off their evaluations might be.”

There is no obvious remedy for the one-two punch of widespread misinformation and a lack of mental tools for evaluating it, but Yeomans said scientists need to do a better job engaging with the public. He and his group regularly address people’s fears regarding near-Earth asteroids by making statements and issuing news releases.

“The hope is that people will understand that we are the more trusted sources of information,” Yeomans said.

In this oblique view, the path of near-Earth asteroid 2012 DA14 is seen passing close to Earth on Feb. 15, 2013. CREDIT: NASA/JPL Near-Earth Object Program Office

And in the case of 2012 DA14, the information is this: There is zero chance of the asteroid hitting Earth next year. The chance of a collision is slightly higher — 1 in 80,000 — when it swings past in 2020, but radar and optical observations of the space rock during next year’s flyby will help the scientists nail down its trajectory, which will in all likelihood reduce the 2020 risk estimate to zero.

There are better things to worry about even than the absolute worst-case scenario. If observations next year show that current estimates are way off and the asteroid and Earth are on track to collide in 2020, then NASA would try to deflect it by bumping it with a space probe sometime before then — a move Yeomans says is doable.

Even if that failed, any Earthbound asteroid has a 70 percent chance of plunging into the ocean, and a much higher chance still of impacting only an ocean or an unoccupied land region.

An asteroid this size strikes Earth every 700 years or so, Yeomans said. Humanity has survived innumerable such events.

This story was provided by Life’s Little Mysteries, a sister site to SPACE.com. Follow Natalie Wolchover on Twitter @nattyover and Life’s Little Mysteries on Twitter @llmysteries, then join us on Facebook.

Richard A. Lovett
for National Geographic News
Published March 15, 2011

The magnitude 9.0 earthquake that struck Japan last Friday was powerful enough to shorten Earth’s day by 1.8 microseconds and throw an extra 6.7 inches (17 centimeters) into the planet’s wobble, scientists say.

That doesn’t mean shockwaves from the event somehow knocked Earth off its north-south axis, around which the planet revolves.

Instead the quake shifted what’s called Earth’s figure axis, an imaginary line around which the world’s mass is balanced, about 33 feet (10 meters) from the north-south axis.

Earth naturally wobbles slightly as it spins, because shifting surface mass such as melting glaciers and moving ocean currents can throw the planet off balance.

Data from high-precision GPS instruments show that parts of Japan shifted by as much as 13 feet (4 meters) as the fault plates lurched due to the earthquake. This allowed scientists to calculate how much Earth’s overall mass distribution had shifted and thus how much the wobble was affected.

The shifting mass also affected the planet’s spin rate, according to geophysicist Richard Gross, of NASA’s Jet Propulsion Laboratory in Pasadena, California. He compares what happened to a figure skater pulling her arms closer to her body, causing her to spin faster.

Because Earth is big, the effect is tiny—a microsecond is only a millionth of a second. For most of us, Gross said, “it has no real practical consequence.”

Researchers are more intrigued by the change in Earth’s wobble, which could inform future space missions, and the data collected on small earthquakes leading up to the main event, which may help with earthquake prediction.

Japan Earthquake Data “Unbelievably Good”

Similar changes to Earth’s mass distribution were calculated from GPS data obtained during the 2004 Sumatra earthquake and the 2010 Chile earthquake. In the case of Sumatra, the change in the length of the day was larger: 6.8 microseconds.

But for the Japan earthquake, the change in Earth’s wobble was more than twice as large as those calculated for the 2004 and 2010 events.

That’s exciting, Gross said, because the wobble is large enough that scientists might actually be able to measure it, not just calculate it, by looking for small changes to Earth’s tilt.

Still, since other factors also redistribute mass in the form of air and water, random changes to Earth’s wobble might mask the effect of the earthquake.

Other geophysicists say that there are even more exciting things that can be done with the GPS data from the Japan earthquake.

For example, Japanese GPS instruments, strain meters, and seismometers recorded dozens of smaller quakes leading up to the main event, said Ken Hudnut, a geophysicist at the U.S. Geological Survey’s Pasadena office.

Scientists poring over the data will be trying to figure out if there was anything unusual in the prior earthquakes that might have indicated they were foreshocks to a bigger event, rather than more ordinary tectonic rumblings.

“The question is, did the GPS or strain meters show a precursor,” Hudnut said. “Because if they did, it will revolutionize earthquake research forever.”

In Sumatra, Hudnut added, the GPS data was “pretty good.” In Chile it was “much better,” and for Japan, the positioning and nature of the instruments made the data “unbelievably good.”

“We may not get another data set like this until I don’t know when. Here, we have a monster earthquake not too far offshore, and GPS instruments along the coast,” he said.

“So much of what scientists do is about getting the right instruments in the right position to record some natural phenomenon, so we can understand it better. If there was anything precursory associated with those foreshocks, it should have been seen on that array of instruments.”

Earth’s wobble calculations aren’t relevant to this particular quest, NASA’s Gross said, but they are more than just a curiosity. Understanding Earth’s spin movement is critical in space launches, for instance.

“When we navigate spacecraft to land a rover on Mars, we have to be able to account for changes in the Earth’s rotation in order to [launch so that we] precisely land the rover where we want to,” he said. “If we didn’t, we might miss Mars altogether.”